3<\/sub><\/p>\nQuestion 15:<\/strong> Give equation and indicate briefly, how will you prepare crystals of zinc sulphate from zinc filings ?
\nAnswer:<\/strong> Take about 50 cm3<\/sup> of dilute sulphuric acid in a beaker and add 5 gm of zinc filings and heat it on a wire gauge with constant stirring. Zinc metal reacts with dilute sulphuric acid to liberate hydrogen gas and zinc sulphate is formed.
\nZn + H2<\/sub>SO4<\/sub> —> ZnSO4<\/sub>\u00a0(Zinc sulphate) + H2<\/sub>
\nMore zinc filings are added, till dilute sulphuric acid is completely consumed and effervescence of hydrogen stops. Filter the solution to remove undissolved zinc and collect the filtrate in an evaporating dish. Heat the solution till a saturated solution is obtained. Cool the solution to obtain the crystals of zinc sulphate with seven molecules of water of crystallization.
\nZnSO4<\/sub> + 7H2<\/sub>O —> ZnSO4<\/sub>.7H2<\/sub>O (Heptahydrate zinc sulphate)<\/p>\nQuestion 16:<\/strong> Give equations and indicate briefly the procedure, you would adopt to prepare :
\n(i) Crystals of ferrous sulphate from iron filings.
\n(ii) Crystals of zinc sulphate from zinc carbonate.
\n(iii) Copper (II) carbonate from copper (II) sulphate.
\nAnswer:<\/strong> (i) Take about 50 cm3<\/sup> of dilute sulphuric acid in a beaker and heat it on a wire gauge. Add iron fillings with constant stirring till effervescence of hydrogen stops. Filter to remove excess of iron fillings and evaporate the solution till a saturated solution is formed. Cool the solution, the crystals of ferrous sulphate are separated.
\nFe + H2<\/sub>SO4<\/sub> —> FeSO4<\/sub> + H2<\/sub>.
\n(ii) Take about 5 gm of zinc carbonate in a beaker, add dilute sulphuric acid and heat till whole of zinc carbonate is dissolved and effervescence of carbon dioxide stops. Filter the solution m an evaporating dish and heat it till a saturated solution is formed. Allow to cool the solution to obtain the crystals of zinc sulphate.
\nZnCO3<\/sub> + H2<\/sub>SO4<\/sub> —> ZnSO4<\/sub> + H2<\/sub>O + CO2<\/sub>
\nZnSO4<\/sub> + 7H2<\/sub>O —> ZnSO4<\/sub>.7H2<\/sub>O (Hydrated zinc (II) sulphate)
\n(iii) Take about 5 gm of copper (II) sulphate in a beaker and dissolve it in water. Now add a concentrated solution of sodium carbonate to this solution. A light blue precipitate of copper (II) carbonate is obtained. Filter the solution, the sodium sulphate passes into the filtrate and the blue precipitate of copper carbonate is obtained as a residue on the filter paper.
\nCuSO4<\/sub> + Na2<\/sub>CO3<\/sub> —> CuCO3<\/sub> + Na2<\/sub>SO4<\/sub> (Light blue colour)<\/p>\nQuestion 17:<\/strong> Name, from the list of substances given below, the substance which you would use to prepare each of the following salts named in Part (i) to (iv).
\nThe substances are:
\nDilute sulphuric acid, copper, lead, dilute nitric acid, dilute hydrochloric acid, copper oxide, lead carbonate, sodium carbonate, sodium and zinc.
\n(i) Lead sulphate. (ii) Copper sulphate.
\n(iii) Sodium sulphate. (iv) Zinc sulphate.
\n(v) What are the two steps necessary to change lead carbonate into lead chloride ?
\n(vi) Give the name of a soluble lead salt and write the equation for the action of heat on this salt.
\nAnswer:<\/strong> (i) For lead sulphate lead carbonate and dilute sulphuric acid are required.
\n(ii) For copper sulphate copper oxide and dilute sulphuric acid are required.
\n(iii) For sodium sulphate sodium carbonate and dilute sulphuric acid are required.
\n(iv) For zinc sulphate zinc and dilute sulphuric acid are required.
\n<\/p>\nQuestion 18:<\/strong> Name the method used for preparation of the following salts from the list given below :
\n(i) Sodium nitrate (ii) Iron (III) chloride
\n(iii) Lead chloride (iv) Zinc sulphate
\n(v) Sodium hydrogen sulphate
\nList:
\n(a) Simple displacement (b) Neutralization
\n(c) Decomposition by acid (d) Double decomposition
\n(e) Direct synthesis.
\nAnswer:<\/strong> (i) (B) Neutralisation (ii) (E) Direct synthesis
\n(iii) (D) Double decomposition (iv) (A) Simple displacement
\n(v) (C) Decomposition by acid.<\/p>\nQuestion 19:<\/strong> Name three classes of substances, which react with an acid to form salts. Write equations to describe their reactions with suitable acids.
\nAnswer:<\/strong> Three different classes of substances are a metal, a base and a metallic carbonate, which react with an acid to form salts.
\n(i) Zinc, a metal reacts with dilute sulphuric acid to form zinc sulphate and hydrogen gas is liberated.
\nZn + H2<\/sub>SO4<\/sub> —> ZnSO4<\/sub> + H2<\/sub>
\n(ii) Sodium hydroxide, a base reacts with dilute nitric acid to form sodium nitrate and water.
\nNaOH + HNO3<\/sub> —> NaNO3<\/sub> + H2<\/sub>O
\n(iii) Magnesium carbonate a metallic carbonate reacts with dilute hydrochloric acid to form magnesium chloride, water and carbon dioxide gas is liberated.<\/p>\nQuestion 20:<\/strong> Making use only of substances chosen from those given below:
\nGive the equations for the reactions by which you could obtain:
\n(i) Hydrogen (ii) Sulphur dioxide
\n(iii) Carbon dioxide (iv) Zinc carbonate
\nAnswer:<\/strong>
\n<\/p>\nQuestion 21:<\/strong> Which of the following salts give acidic solutions, alkaline solutions, and neutral solutions in water:
\npotassium nitrate, KNO3<\/sub>; ammonium sulphate, (NH4<\/sub>)2<\/sub>SO4<\/sub>; potassium carbonate, K2<\/sub>CO3<\/sub>; sodium chloride, NaCl; sodium acetate, CH3<\/sub>COONa; and copper sulphate, CuSO4<\/sub>.
\n(i) Acidic solutions ………………………………………………..
\n(ii) Alkaline solutions …………………………………………….
\n(iii) Neutral solutions …………………………………………….
\nAnswer:<\/strong> (i) Acidic solutions: ammonium sulphate; (NH4<\/sub>)2<\/sub>SO4<\/sub>, copper sulphate (CuSO4<\/sub>).
\n(ii) Alkaline solutions: potassium carbonate; (K2<\/sub>CO3<\/sub>), sodium acetate (CH3<\/sub>COONa).
\n(iii) Neutral solutions: potassium nitrate; (KNO3<\/sub>), sodium chloride (NaCl).<\/p>\nQuestion 22:<\/strong> (i) Name four soluble salts<\/a>.
\n(ii) Name four insoluble salts.
\nAnswer:<\/strong> (i) (a) Zinc sulphate. (b) Iron (II) sulphate.
\n(c) Copper (II) sulphate. (d) Sodium sulphate.
\n(ii) (a) Calcium carbonate. (b) Lead sulphate.
\n(c) Silver chloride. (d) Barium sulphate.<\/p>\nQuestion 23:<\/strong> (i) What happens to the crystals of washing soda when exposed to air ? Name the phenomenon exhibited.
\n(ii) Classify the following compounds into: Deliquescent, Efflorescent, None of these (a) Magnesium chloride crystals, (b) Zinc chloride crystals,
\n(c) Lead nitrate crystals, (d) Ferrous sulphate crystals,
\n(e) Lead chloride, (f) Copper sulphate crystals,
\n(g) Zinc hydroxide, (h) Magnesium chloride.
\nAnswer:<\/strong> (i) When exposed to air washing soda crystals lose their water of crystallisation and become amorphous.
\n\u2234 \u00a0 The phenomenon is called efflorescence.
\n(ii) (a) Deliquescent (b) Deliquescent (c) None of these
\n(d) None of these (e) None of these (f) Efflorescent
\n(g) None of these (h) Highly deliquescent.<\/p>\nQuestion 24:<\/strong> Answer the questions given below, relating your answers only to salts given in the following list: Sodium chloride, calcium chloride, copper sulphate.5-water.
\n(i) What name is given to the water in compound copper sulphate. 5-water ?
\n(ii) If copper sulphate. 5-water is heated, the water is driven off leaving anhydrous copper sulphate.
\n(a) What is the colour of anhydrous copper sulphate ?
\n(b) By what means, other than heating, could you dehydrate copper sulphate. 5-water and obtain anhydrous copper sulphate ?
\n(iii) What is deliquescence.
\n(iv) Which one of the salts in the given list is deliquescent ?
\nAnswer:<\/strong> (i) Water of crystallization.
\n(ii) (a) White. (b) By adding cone. H2<\/sub>SO4<\/sub>.
\n(iii) Compounds that take up enough water from the air to dissolve in the water, are called deliquescent, e.g. Calcium chloride (CaCl2<\/sub>) and sodium hydroxide are deliquescent.
\n(iv) Calcium chloride.<\/p>\nQuestion 25:<\/strong> CuSO4<\/sub>.5H2<\/sub>0, Na2<\/sub>CO3<\/sub>.10H2<\/sub>O, CaO and anhydrous calcium chloride are chemicals commonly available in laboratory. Answer the following questions relating your answer to the list of chemicals given above.
\n(i) Which salt is blue in colour ? (ii) Which salt is efflorescent in nature ?
\n(iii) Which salt is hydroscopic in nature ? (iv) Which salt is deliquescent in nature.
\n(v) State your observations when solution of calcium chloride is mixed with solution of sodium carbonate.
\nAnswer:<\/strong> (i) CuSO4<\/sub>. 5H2<\/sub>O is blue in colour.
\n(ii) Na2<\/sub>CO3<\/sub>.10H2<\/sub>O is efflorescent in nature.
\n(iii) CaO is hydroscopic in nature.
\n(iv) Anhydrous calcium chloride is deliquescent in nature.
\n(v) A white ppt. of calcium carbonate appears when the solutions of CaCl2<\/sub> and Na2<\/sub>CO3<\/sub> are mixed. The white ppt. gradually settles at the base of test tube.<\/p>\nQuestion 26:<\/strong> Answer the following questions, relating your answers only to salts in the list given below :
\nAnhydrous calcium chloride, copper sulphate. 5H2<\/sub>O, sodium carbonate. 10-water.
\n(i) Which compound is efflorescent ?
\n(ii) Which compound is blue in colour ?
\n(iii) Which compound is deliquescent ?
\n(iv) What would be seen on mixing a solution of calcium chloride with a solution of sodium carbonate ?
\n(v) Write the balanced equation for the reaction occuring when a solution of calcium chloride is mixed with a solution of sodium carbonate.
\nAnswer:<\/strong> (i) Sodium carbonate. 10-water.
\n(ii) Copper sulphate. 5H2<\/sub>O.
\n(iii) Anhydrous calcium chloride.
\n(iv) A white precipitate of calcium carbonate is seen.
\n(v) CaCl2<\/sub>(aq.) + Na2<\/sub>CO3<\/sub> (aq.) —> CaCO3<\/sub> (White ppt) + 2NaCl (aq.)<\/p>\nQuestion 27:<\/strong> (i) Give chemical names of the following:
\n(a) Green vitriol (b) Blue vitriol (c) White vitriol.
\n(ii) State the colour of the following salts:
\n(a) Copper chloride (b) Ferric chloride
\n(c) Copper nitrate (d) Lead nitrate
\n(e) Magnesium carbonate (f) Zinc hydroxide
\n(iii) State the colours of the aqueous solution of the following salts:
\n(a) Calcium sulphate crystals (b) Ferrous chloride crystals
\n(c) Ferric chloride crystals (d) Ferrous sulphate crystals
\n(e) Ferric sulphate crystals (f) Copper sulphate crystals.
\nAnswer:<\/strong> (i) (a) Green vitriol\u2014Ferrous sulphate,
\n(b) Blue vitriol\u2014Copper sulphate
\n(c) White vitriol\u2014Zinc sulphate.
\n(ii) (a) Brown (anhydrous) (b) Black (anhydrous) (c) Blue
\n(d) White (e) White (f) White
\n(iii) (a) Colourless (b) Blue green (c) Yellow
\n(d) Green (e) Yellowish white (f) Blue.<\/p>\nFigure\/Table Based Questions<\/span><\/h3>\nQuestion 1:<\/strong> Draw the structure of the stable positive ion formed when an acid dissolves in water.
\nAnswer:<\/strong>
\n<\/p>\nQuestion 2:<\/strong> Some methods used for the laboratory preparation of salts are :
\nA : metal + acid
\nB : carbonate + acid
\nC : precipitation (double decomposition)
\nD : direct combination
\nE: titration
\nCopy and complete the following table:<\/p>\n\n\n\nSalt<\/td>\n | Method of Preparation<\/td>\n<\/tr>\n |
\nAmmbnium sulphate<\/p>\n Calcium carbonate<\/p>\n Iron (III) chloride<\/p>\n Lead nitrate<\/p>\n Zinc sulphate<\/td>\n | <\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n |